This invention relates to a coolant feeding device of a machine tool.
Prior art references (such as the Japanese Patent Publication No. 66437 of 1997) have disclosed machine tools that feed coolant from a coolant feed pump to a mist generating device at the tip of a spindle through a coolant feed line, and that is provided with a valve path at a coolant inflow portion of the mist generating device. Here, the valve means is to close a coolant path when coolant pressure within the feed line lowers below a fixed level.
In the above conventional machine tools, compressed air is mingled with the coolant inside the feed line. When the feed pump stops feeding the coolant, compressed air pressure lowers, and then the air expands, thereby causing a little coolant leakage out of the valve path (this phenomenon is called liquid dropping).
The liquid dropping is a waste of coolant. Besides, when generating mist again, the coolant which remains in the mist generating device may spout outside at a stretch, thereby polluting a work piece and a working environment.
An object of this invention is to provide a coolant feeding device of the machine tool that can solve the above problems.
The present invention discloses a coolant feeding device of a machine tool that feeds coolant to a mist generating device at the tip of a spindle through a coolant feed line. Besides, a coolant forcing means is provided to the tip of the spindle near the mist generating device to force out the coolant inside a cylinder chamber through a valve path.
Since the coolant forcing means is located near the mist generating device, air remaining in coolant between the coolant forcing means and the mist generating device is very small in quantity, even if many air grains are mixed into the coolant to be fed into the mist generating device. Accordingly, when the coolant forcing means finishes forcint out coolant, the valve path is immediately closed without any influence of the air grains, thereby preventing the coolant inside the feed line from leaking into the mist generating device.
Specifically, the machine tool of this invention supplies coolant from a coolant feed pump to a mist generating device at the tip of a spindle through a coolant feed line. Besides, a coolant forcing means is provided to the tip of the spindle near the mist generating device to force out the coolant inside a cylinder chamber through a valve path. The coolant inside the feed line is repeatedly fed into the cylinder chamber, whereas the coolant forced out from the cylinder chamber is fed into the mist generating device at proper pressure.
According to this structure, a fixed amount of coolant can be fed to the mist generating device properly and intermittently by forcing out coolant from the cylinder chamber.
Moreover, in the present invention, a fixed amount of coolant inside the feed line flows into the cylinder chamber, when the coolant pressure inside the feed line is below a fixed level. On the other hand, the coolant inside the cylinder chamber is forced out to the mist generating device at proper pressure, when the coolant pressure inside the feed line is over a fixed level.
According to this structure, since the coolant forcing means works in connection with a change of the coolant pressure inside the feed line, a proper amount of coolant can be timely fed into the mist generating device by controlling the feed pump.
The present invention is more preferable with the following structure. When the coolant pressure inside the feed line is below a fixed level, a piston forming the cylinder chamber is displaced in a fixed direction by spring force, and a fixed amount of coolant from the feed line flows into the cylinder chamber due to displacement of the piston. On the other hand, when the coolant pressure inside the feed line is over a fixed level, the piston is displaced in a reverse direction to the above fixed direction, and the coolant from the cylinder chamber is forced out to the mist generating device at proper pressure due to reverse displacement of the piston.
According to this structure, the piston is driven only by the spring force and the coolant pressure inside the feed line, thereby effecting simple mechanism of driving the piston.